Tool locking apparatus for machine hammers

ABSTRACT

In the front head (11) of a machine hammer (10), transversely disposed wedges (18) are adapted to lock the working tool (12) so that the working tool (12) is axially movable by form-restricted cooperation with recesses (16) on the working tool (12). Each wedge (18) is locked in the front head (11) by a key (20), which extends across the wedge (18) into engagement with a transverse bore (21) therein. The key (20) has a releasable locking device including a locking element affixed in the front head (11) and formed by a polyurethane block (24). The block (24) is provided with a through bore (27) and has elastically form-recovering material properties. When, for purposes of locking the key (20), the key (20) is pressed through the bore of the block (24), the block (24) is caused to expand resiliently into an annular groove (22) on the key (20), thereby locking the key (20) in the front head (11) and providing its wedge (18) locking function. In use of two wedges (18), one single key (20) is set to lock both wedges (18) and is locked by one single block (24).

BACKGROUND OF THE DISCLOSURE

The present invention relates to a tool locking apparatus for machinehammers of the type having a front head with an impact deliveringworking tool carried axially movably therein, at least one wedgedisposed transversely in the front head and insertable intoform-restricted engagement with a side recess in the working tool inorder to limit the axial movability of and lock the working toolrelative to the front head, and a key axially insertable transverselyinto the front head to extend across the the wedge and retain the wedgein a position locking the working tool.

In this predominantly heavy type of machinery, the demands concerningsafe locking of the working tool in the machine housing are very high. Atool which falls out, for instance when penetrating a concrete vault,can cause considerable material damage, and above all, can lead toserious personal injury. In larger mostly hydraulically driven types ofmachine hammers, it is not unusual that the weight of the working toolreaches 130 kg, which underlines the danger. Simultaneously there isalso the demand that changes between different types of tools, forexample breaking tools, chisels, spades and rams, under active fieldservice conditions can be made as quickly as possible.

In earlier constructions applicant has himself made use of spring loadedpins for locking the wedges. Wear study indicates, that impact wavesduring work of the machine hammer via the wedges are transmitted to thepins, tend to urge them into an oblique position due to their shortguiding length, and lead to increased wear. Worn wedges and damaged pinscan be replaced by exchange, while wear of the machine housing affects amain component which cannot be looked at as a spare part. Furthermore,there is the risk of broken springs endangering safe locking of thewedges. An alternative earlier suggestion known to applicant, whichconsisted in locking the wedges by engagement with spring loadedsleeves, was in the long run similarly liable to wear and fatigue of thesprings.

In the type of machine hammers stated by way of introduction above, andin particular concerning heavy, preferably hydraulically driven machinesto be mounted on booms of mobile working machinery, the object of thepresent invention is to create a locking means able to offer increasedsafety against the tool falling out from the machine during operation,and to allow easier handling when changing the tool under fieldconditions. These objects are achieved by the apparatus defined in theclaims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail hereinafter withreference to the accompanying drawing. FIG. 1 of the drawing shows apartial longitudinal section through the forward portion of a machinehammer embodying the invention. FIG. 2 shows a cross section on the line2--2 in FIG. 1. FIG. 3 is a side view of the front head viewed in thedirection of arrows 3--3 in FIG. 1.

DETAILED DESCRIPTION

The machine hammer 10 in FIG. 1 carries a front head 11 in which aworking tool 12, for example a breaking tool, is axially movably guidedin a tool sleeve 13, suitably made of steel and strongly press fitted inthe front head 11. When starting the machine, the movability of theworking tool 12 is supported by lubricating grease, portion-wisesupplied via ring grooves and lubricating passages 15, 17 to theinterior of the tool sleeve 13. In a conventional way, not illustratedin FIG. 1, a suitably hydraulically driven reciprocating hammer piston14 delivers impact energy to the working tool 12. Diametrically opposedside recesses 16 are provided in the working tool 12 and wedges 18,carried in the front head 11, extend transversely to the working tool 12into the recesses 16 which by form-bound engagement at their oppositeends are adapted to limit the axial movement of the working tool 12,thereby retaining the tool 12 in the front head 11 and hindering it fromfalling out. In the present instance the wedges 18, as usual in case ofheavier machines, are formed with an oblong cross-section and parallelsemicylindrical shorter sides. In smaller machines circularlycylindrical wedges may be used as well.

The front piece 11 comprises a pair of parallel bores or oval channels19 into which the wedges 18 can be pushed axially in order to lock theworking tool 12. A side bore 26 is formed in the front head 11, whichcentrally intersects and and crosses the channels 19, and a key 20 isinsertable thereinto and led through aligned cross-bores 21 in thewedges 18. In case of circularly cylindrical wedges 18, such wedgesshould be turned to bring the cross-bores 21 into alignment with theside bore 26. The key 20 locks the wedges 18 in working position in thefront head 11.

The key 20, however, has a tendency to to be shaken out of the side 26bore during impacting work, and must be locked in the front head 11 byan arresting element allowing safe looking and concurrent simple andquick release of such locking. To this end the key 20, according to theinvention, is looked in an improved way, form-bound in the front head 11by releasable engagement with a locking element made of a materialhaving elastically form-recovering property, suitably of plasticmaterial and preferably of polyurethane. The form-bound engagement canbe achieved by a locking element disposed sidewise adjacent to the thekey 20 in the front head 11 which by a tongue is laterally engageablewith a ring groove in the key 20 (not shown in the drawing). A safer wayof locking, however, can be achieved if the locking element is formed asa die-like block 24 of polyurethane with a central through bore 27 of asomewhat smaller diameter than the diameter of the key 20. The block 24is inserted in a milled slot 23 in the front head 11 and can be lockedtherein by a locking pin 25, for example in the form of a hollow slitspring sleeve. The slot 23 intersects the side bore 26 of the key 20 andin locking position the bore 27 of the block 24 is disposed coaxiallywith the side bore 26. The key 20 has an annular waist-groove 22 with areduced diameter in comparison with the remainder of key 20 andcorresponding to the inner diameter of the block 24.

With the wedges 18 in place in working position as in FIG. 2, andinserted to place the cross-bores 21 in substantially coaxial relationto the side bore 26, the key 20 is set thereinto and pressed through thebore 27 of the locking element or block 24 until the latter snaps intothe waist-groove 22 and locks the key 20. When disassembling the wedges18 in order to change the tool, the key 20 is first pressed out from theblock 24 and the side bore 26 so that the wedges 18 then readily can beremoved.

In machine hammers of lesser power, when a one-sided locking of theworking tool 12 by a single wedge 18 will suffice, or if, as analternative to the construction shown in FIG. 2, there is desired toallot a key 20 to each of wedges 18, it will be evident, that a lockingelement similar to the block 24 affixed in the front head 11 would haveto be allotted to the key 20 at hand, or to each of the two keys 20, inwhich cases key-locking will achieved by form-bound cooperation with aring-groove arranged in suitable position on each key.

Furthermore, at lesser power, it may be sufficient to lay the key 20across an outer notch on a coacting wedge 18 instead of mating the key20 with a through bore 21 in the wedge 18.

We claim:
 1. A tool locking apparatus for machine hammers (10) having afront head (11) with an impact delivering working tool (12) carriedaxially movably therein, the apparatus further comprising:at least onewedge (18) disposed transversely in the front head (11) and insertableinto form-restricted engagement with a side recess (16) in the workingtool (12) in order to limit the axial movability of and lock the workingtool (12) relative to the front head (11), and a key (20) axiallyinsertable transversely into the front head to extend across the wedge(18) and retain the wedge (18) in a position that locks the working tool(12), wherein the key (20) is locked in the front head (11) byreleasable form-bound engagement with a locking element (24) of amaterial having elastically form-recovering properties.
 2. A toollocking apparatus according to claim 1, wherein the locking elementcomprises a block (24) of plastic material having said resilientlyform-recovering properties, said block (24) being provided with athrough bore (27) to be penetrated by the key (20) when the key (20) isinserted into the front head (11) crosswise relative to the wedge (18),the locking element (24) thus being forcibly expanded around the key(20) and recovering resiliently to a locking position around and into anannular groove (22) provided on the key (20).
 3. A tool lockingapparatus according to claim 1, wherein the locking element (24)comprises a block (24) of polyurethane.
 4. A tool locking apparatusaccording to claim 2, wherein the key (20) is adapted to secure two saidwedges (18) provided at opposite sides of the working tool (12), the key(20) crossing the wedges (18) by extending through coaxially alignableopenings (21) in the wedges (18).
 5. A tool locking apparatus accordingto claim 4, wherein the locking element block (24) is affixed in a slot(23) in the front head (11) with its bore (27) disposed in a position inrespect to which the openings (21) of the wedges (18) can be orientedcoaxially.
 6. A tool locking apparatus according to claim 5, whereinsaid locking element block (24) is arranged intermediate the wedges (18)in the front head (11) and by its bore (27) cooperates with said annulargroove (22) in the key (20).
 7. A tool locking apparatus according toclaim 2, wherein:the front head (11) comprises first and second mutuallyparallel channels (19) for insertion of one said wedge (18) into each ofsaid channels, the front head (11) has a side bore (26) for the key(20), which side bore (26) intersects the channels (19), transversethrough bores (21) are provided in the wedges (18) and are equal in sizeand alignable with the side bore (26) in the front head (11), and thelocking element (24) is provided in the front head (11) with the bore(27) of the locking element (24) in coaxial relation to the side bore(26) for the key (20).
 8. A tool locking apparatus according to claim 2,wherein:the front head (11) comprises a first channel (19) for theinsertion of a wedge (18) and has a side bore (26) for the key (20) thatintersects the channel (19), a transverse through bore (21) is providedin the wedge (18) and is equal in size and alignable with the side bore(26) in the front head (11), and the locking element (24) is provided inthe front head (11) with the bore (27) of the locking element (24) incoaxial relation to the side bore (26) for the key (20).
 9. A toollocking apparatus according to claim 2, wherein the locking element (24)comprises a block (24) of polyurethane.
 10. A tool locking apparatusaccording to claim 1, wherein the key (20) is adapted to secure two saidwedges (18) provided at opposite sides of the working tool (12), the key(20) crossing the wedges (18) by extending through coaxially alignableopenings (21) in the wedges (18).
 11. A tool locking apparatus accordingto claim 3, wherein the key (20) is adapted to secure two said wedges(18) provided at opposite sides of the working tool (12), the key (20)crossing the wedges (18) by extending through coaxially alignableopenings (21) in the wedges.
 12. A tool locking apparatus according toclaim 9, wherein the key (20) is adapted to secure two said wedges (18)provided at opposite sides of the working tool (12), the key (20)crossing the wedges (18) by extending through coaxially alignableopenings (21) in the wedges (18).
 13. A tool locking apparatus accordingto claim 12, wherein the locking element block (24) is affixed in a slot(23) in the front head (11) with its bore (27) disposed in a position inrespect to which the openings (21) of the wedges (18) can be orientedcoaxially.
 14. A tool locking apparatus according to claim 16, whereinsaid locking element block (24) is arranged intermediate the wedges (18)in the front head (11) and by its bore (27) cooperates with said annulargroove (22) in the key (20).
 15. A tool locking apparatus according toclaim 7, wherein the locking element (24) comprises a block (24) ofpolyurethane.
 16. A tool locking apparatus according to claim 8, whereinthe locking element (24) comprises a block (24) of polyurethane.
 17. Atool locking apparatus according to claim 4, wherein said coaxiallyalignable openings comprise cross-bores (21) in the wedges (18).
 18. Atool locking apparatus according to claim 5, wherein said coaxiallyalignable openings comprise cross-bores (21) in the wedges (18).
 19. Atool locking apparatus according to claim 6, wherein said coaxiallyalignable openings comprise cross-bores (21) in the wedges (18).
 20. Atool locking apparatus according to claim 10, wherein said coaxiallyalignable openings comprise cross-bores (21) in the wedges (18).
 21. Atool locking apparatus according to claim 11, wherein said coaxiallyalignable openings comprise cross-bores (11) in the wedges (18).
 22. Atool locking apparatus according to claim 12, wherein said coaxiallyalignable openings comprise cross-bores (21) in the wedges (18).
 23. Atool locking apparatus according to claim 13, wherein said coaxiallyalignable openings comprise cross-bores (21) in the wedges (18).